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August 29, 2003

African-American Teen Mothers Have Greater Risk for Low-Birth-Weight and Premature Babies

African-American teens are twice as likely to deliver low-birth-weight babies and 1.5 times more likely to have premature babies than whites, according to a study by researchers at the Johns Hopkins Bloomberg School of Public Health. The study, conducted by the School’s Center for Human Nutrition (CHN), examined birth outcomes of 1,120 pregnant African-American teens age 17 and younger, living in Baltimore, Md., and compared them to national data on white women. When compared to pregnant black women of all ages in Maryland, the study found the younger group had almost twice the infant mortality rate (2.3 percent vs. 1.3 percent). The study appears in the August 2003 edition of The Journal of Pediatrics.  

“This study shows the need for effective intervention programs to reduce the risk factors contributing to low birth weight and other poor pregnancy outcomes in this population,” said principal investigator Kimberly O’Brien, PhD, associate professor with CHN and the School’s Department of International Health. “In the long run, it costs more to pay for the health care costs associated with low birth weight and premature babies than to focus on prevention. There’s not enough attention given to this vulnerable group.”  

Babies born weighing less than 5 pounds, 8 ounces, and premature babies born before 37 weeks of gestation may face serious health problems and suffer developmental problems later in life. Babies born to teen mothers of all races are at a higher risk of low birth weight, preterm delivery, and infant mortality, than those born to older mothers. Previous studies have also documented that black women in general have a higher risk of factors associated with adverse pregnancy outcomes than white or Hispanic women. Yet, until now, the risk factors for adverse birth outcomes in black teens had not been well studied. 

Baltimore led the nation with the highest percentage of teens giving birth, with 22.4 percent in 1998, which was nearly twice the national average of 12.5 percent (source: Population Connection, Kid Friendly Cities Report Card, 2002). CHN investigators identified several characteristics and risk factors related to adverse birth outcomes in the group of urban black teens, including low pre-pregnancy body mass index, inadequate weight gain during pregnancy, inadequate utilization of prenatal care, the presence of sexually transmitted diseases, and a history of cigarette smoking.

Nutritional status and weight gain during pregnancy had a significant impact on the risk of preterm birth. Adolescents in the study who were underweight before pregnancy had twice the risk for preterm birth than those of a healthy weight. More than two-thirds of all the study participants did not have appropriate weight gain during pregnancy. Nearly 30 percent gained too little weight and 40 percent gained more than the recommended amount (25-35 pounds for normal-weight women). Those who did not gain adequate weight had three times the risk for preterm birth than those who had appropriate weight gain during pregnancy. 

Inadequate utilization of prenatal care was evident in more than half the girls in the study under age 15 and 35 percent of those ages 15-17. Among these girls, the number of preterm births was twice the national rate. Infant birth weight was also affected by risk- taking behaviors during pregnancy. Girls with a history of cigarette smoking had babies who weighed on average 110 grams less than babies born to non-smokers. Rates of cigarette smoking among blacks is typically lower than white adolescents, but is increasing and is of great concern to the study investigators.

Sexually transmitted diseases were also common in this group. During pregnancy, over 20 percent of the adolescents had chlamydia, nearly 7 percent had gonorrhea, and 30 percent had at least one vaginal infection during pregnancy. No single sexually transmitted disease was associated with preterm delivery or low birth weight, but girls who had a vaginal infection during pregnancy had babies with a slightly decreased birth weight.

“Characteristics and risk factors for adverse birth outcomes in pregnant black adolescents” was written by Shih-Chen Chang, Kimberly O’Brien, Maureen Schulman Nathanson, Jeri Mancini and Frank R. Witter.

Funding for this research study was provided by National Institutes of Health/NICHD.

Public Affairs Media Contacts for the Johns Hopkins Bloomberg School of Public Health: Tim Parsons or Kenna Brigham at 410-955-6878 or paffairs@jhsph.edu.